/* Copyright 2021 The TensorFlow Authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#include <stddef.h>

#include <cstring>

#include "tensorflow/lite/c/builtin_op_data.h"
#include "tensorflow/lite/c/common.h"
#include "tensorflow/lite/kernels/internal/compatibility.h"
#include "tensorflow/lite/kernels/kernel_util.h"
#include "tensorflow/lite/micro/kernels/kernel_util.h"
#include "tensorflow/lite/micro/memory_helpers.h"
#include "tensorflow/lite/micro/micro_error_reporter.h"
#include "tensorflow/lite/micro/micro_graph.h"
#include "tensorflow/lite/micro/micro_resource_variable.h"
#include "tensorflow/lite/schema/schema_generated.h"

namespace tflite {

namespace {

constexpr int kInputVariableId = 0;
constexpr int kInputValue = 1;

TfLiteStatus Prepare(TfLiteContext* context, TfLiteNode* node) {
  TF_LITE_ENSURE_EQ(context, NumInputs(node), 2);
  TF_LITE_ENSURE_EQ(context, NumOutputs(node), 0);

  // This must be a TfLiteEvalTensor despite this being in Prepare, because
  // CreateTensor allocates a temp tensor from the flatbuffer, which does not
  // contain the correct ID generated within the VAR_HANDLE op. EvalTensors are
  // all allocated during StartModelAllocation which happens before
  // init/prepare, and VAR_HANDLE Prepare() references its own op_data in the
  // TfLiteEvalTensor, so reading the ID here is valid.
  const TfLiteEvalTensor* input_resource_id_tensor =
      tflite::micro::GetEvalInput(context, node, kInputVariableId);
  TFLITE_DCHECK(input_resource_id_tensor != nullptr);
  TF_LITE_ENSURE(context, (input_resource_id_tensor->type == kTfLiteResource ||
                           input_resource_id_tensor->type == kTfLiteInt32));
  TF_LITE_ENSURE_EQ(context, NumElements(input_resource_id_tensor->dims), 1);

  const TfLiteTensor* input_value = GetInput(context, node, kInputValue);
  TFLITE_DCHECK(input_value != nullptr);

  // Casting to TfliteIntArray is required since we are re-using
  // GetExecutionPlan from TfLiteContext. On TFLM this method returns a
  // MicroGraph.
  // TODO(b/188226309): Design a cleaner way to get a graph from kernel context.
  MicroGraph* graph_info;
  context->GetExecutionPlan(context,
                            reinterpret_cast<TfLiteIntArray**>(&graph_info));
  MicroResourceVariables* resources = graph_info->GetResourceVariables();
  TF_LITE_ENSURE_OK(context,
                    resources->Allocate(input_resource_id_tensor->data.i32[0],
                                        context, input_value));

  return kTfLiteOk;
}

TfLiteStatus Eval(TfLiteContext* context, TfLiteNode* node) {
  const TfLiteEvalTensor* input_id =
      tflite::micro::GetEvalInput(context, node, kInputVariableId);
  TFLITE_DCHECK(input_id != nullptr);

  const TfLiteEvalTensor* input_value =
      tflite::micro::GetEvalInput(context, node, kInputValue);
  TFLITE_DCHECK(input_value != nullptr);

  // Casting to TfliteIntArray is required since we are re-using
  // GetExecutionPlan from TfLiteContext. On TFLM this method returns a
  // MicroGraph.
  // TODO(b/188226309): Design a cleaner way to get a graph from kernel context.
  MicroGraph* graph_info;
  context->GetExecutionPlan(context,
                            reinterpret_cast<TfLiteIntArray**>(&graph_info));
  MicroResourceVariables* resources = graph_info->GetResourceVariables();
  if (resources == nullptr) {
    MicroPrintf(
        "ASSIGN_VARIABLE requires resource variables. Please create "
        "ResourceVariables and pass it to the interpreter.");
    return kTfLiteError;
  }
  TF_LITE_ENSURE_OK(context,
                    resources->Assign(input_id->data.i32[0], input_value));
  return kTfLiteOk;
}

}  // namespace.

TfLiteRegistration Register_ASSIGN_VARIABLE() {
  return {/*init=*/nullptr,
          /*free=*/nullptr,
          /*prepare=*/Prepare,
          /*invoke=*/Eval,
          /*profiling_string=*/nullptr,
          /*builtin_code=*/0,
          /*custom_name=*/nullptr,
          /*version=*/0};
}

}  // namespace tflite